Rod de-tensioning device and methods of operating the same

ABSTRACT

A rod detensioning unit including a gripping unit removal device that engages a gripping unit on a rod, a chair frame configured to engage a rod, a rod tensioning unit that applies tension to an external portion of the rod to remove load from the gripping unit, a load cell unit that measures a tension level applied to the rod by the tensioning unit, a plate gripping unit that engages the rod and secures the chair frame, rod tensioning unit, load cell and plate gripping unit to the rod, a drive unit that engages the gripping unit removal device, and an extension unit affixed to the external portion of the rod when the original external rod length is too short to accommodate the de-tensioning unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Non-Provisional patentapplication Ser. No. 15/590,490, entitled “ROD DE-TENSIONING DEVICE”filed on May 9, 2017, which claims priority to U.S. Provisional PatentApp. No. 62/335,362, entitled “ROD DE-TENSIONING DEVICE AND METHODS OFOPERATING THE SAME” filed on May 12, 2016, which is incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

Post-tensioned trunnion anchor rods are used to secure large devices,such as gates on dams, to structures. To firmly secure the devices tothe structure, tension is applied to the trunnion rods, and theindividual rods are locked off to maintain the tension load within therod. See, U.S. Pat. No. 2,705,871 to Kenigsberg and U.S. Pat. No.2,871,664 to Dobson. For large structures, such as dams, a large amountof tension (typically 60% or more of its ultimate strength) is appliedto the rods creating a potentially dangerous situation. At least 100-200dams in the United States use post-tensioned trunnion rods for gateanchorages. Trunnion rods are predominately made of metal that isdesigned to operate at a specific tension level. Increased tension, inaddition to long-term environmental stresses in the rods creates adangerous situation where the rods may fail in a brittle and abruptmanner before the end of life expectancy date.

Since 1960 many dams were built using post-tensioned trunnion rods. Atthe time the dams were erected, and until 2010, cost-effective and safetechnology to determine the amount of tension in each rod was notavailable, and premature rod failures due to over-tensioning haveoccurred on several dams since the 1970s. Because of the importance ofthese trunnion rods, and the aging of the inventory of rods currently indams, dam owners and operators are beginning to regularly test thetension in each rod and the integrity of the rods usingrecently-developed non-destructive techniques that are safe and costefficient.

However, even with the testing, there is currently no safe or efficientprocedure to remove excess tension in trunnion rods. In a damenvironment, an abrupt failure of a post-tensioned trunnion rod canresult in the trunnion rod being expelled from the dam at high rate ofspeed. Further, the costs involved with removing and replacing trunnionrods, or otherwise reinforcing gate anchorages on dams are very high.Therefore, a need exists for a method of removing excess tension frompost-tensioned trunnion rods to increase the useful life of installedtrunnion rods.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present disclosure includes a rod detensioningunit including a gripping unit removal device that engages a grippingunit on a rod, a chair frame configured to engage a rod, a rodtensioning unit that applies tension to an external portion of the rodto remove load from the gripping unit, a load cell unit that measures atension level applied to the rod by the tensioning unit, a plategripping unit that engages the rod and secures the chair frame, rodtensioning unit, load cell and plate gripping unit to the rod, a driveunit that engages the gripping unit removal device, and an extensionunit affixed to the external portion of the rod when the originalexternal rod length is too short to accommodate the de-tensioning unit.

In another embodiment, the gripping unit includes an opening sized toaccommodate the rod.

In another embodiment, the opening has an inner surface that includes aplurality of threads.

In another embodiment, the rod detensioning unit includes a secondgripping unit that is in the opening of the gripping unit.

In another embodiment, the second gripping unit includes a plurality ofthreads that correspond to the threads in the opening.

In another embodiment, the second gripping unit is positioned in theopening a predetermined distance from a trunnion.

In another embodiment, the rod tensioning unit is hydraulically driven.

In another embodiment, the rod detensioning unit includes a centralcontrol unit communicatively coupled to the drive unit.

In another embodiment, the rod detensioning unit includes a plurality ofcameras optically coupled to the central control unit.

In another embodiment, at least one camera is positioned to capture animage of a side of the gripping unit.

Another embodiment of the present disclosure includes a method ofdetensioning a rod, the method including removably attaching a grippingunit removal device on a gripping unit where the gripping unit engages arod, positioning a chair frame on the rod over a periphery of thegripping unit, positioning a rod tensioning unit on the rod with a firstend of the rod tensioning unit being in contact with a surface of thechair frame, applying a first force to the rod tensioning unit,positioning a bearing plate on the rod in contact with the rodtensioning unit, positioning a load cell in contact with the rod on therod tensioning unit, securing a drive unit to the chair frame such thata portion of the drive unit is in contact with the rod, applying asecond pressure is applied to the rod tensioning unit, actuating thedrive unit, and releasing the second pressure on the rod tensioningunit.

In another embodiment, the first pressure is sufficient to increase thetension in the rod.

In another embodiment, the second pressure is sufficient to separate thegripping unit from a trunnion.

In another embodiment, the driving unit includes a engagement portionthat is in contact with the rod.

In another embodiment, the drive unit actuates to move the gripping unita predetermined distance from the trunnion.

In another embodiment, the drive unit is electrically driven.

In another embodiment, the method includes the step of connecting acentral control unit communicatively coupled to the drive unit.

In another embodiment, the method includes the step of opticallyconnecting a plurality of cameras to the central control unit.

In another embodiment, at least one camera is positioned to capture animage of a side of the gripping unit.

In another embodiment, the first pressure is less than the secondpressure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. IA depicts a dam that includes a spillway defined between twopiers;

FIG. IB depicts a trunnion rod system used to secure structurestogether;

FIG. 2 depicts a gripping unit installed on a rod;

FIG. 3 depicts a rod de-tensioning device;

FIG. 4 depicts a drive unit 400 on the chair frame;

FIG. 5 depicts the gripping unit moved from an original position on therod to a new position a distance x from the original position;

FIG. 6 depicts a rod de-tensioning control unit;

FIG. 7 depicts a schematic representation of the process ofde-tensioning rods using the de-tensioning system;

FIG. 8 depicts one embodiment of a gripping unit removal device; and

FIG. 9 depicts an arresting unit.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A depicts a dam 100 that includes a spillway 110 defined betweentwo piers 120. Mounted between piers 120 is Tainter gate 130 comprisedof a curved panel 132 supported on radial arms 134. Radial arms 134converge at trunnion pin 136 that is supported at a rotational pivot bytrunnion girders 140. The trunnion girders 140 are separate from thepiers 120 and are secured to the piers 120 by rods 150. Sides of curvedpanel 132 may slide through and engage with curved leak limiting slots122 in side faces of piers 120. It is to be appreciated that a waterreservoir is on the convex or upstream side of curved panel 132. Whengate 130 is closed the panel is in the lower position as shown in FIG.1A and water is prevented from flowing downstream over the dam by curvedpanel 132. When gate 130 is opened by rotating radial arm structure 134about trunnion pin 136, water from the reservoir is permitted to flowunder panel 132, over spillway 110, and downstream from dam 100.

Trunnion girders 140 may be vertically supported on ledges 124 that areformed on piers 120. Trunnion pins 136 are journaled in trunnion girders140. Tension rods or anchorage tendons 150 extend in a generallyupstream direction into piers 120 and are anchored in the piers bytendon anchorage plates or anchorage means 152 embedded in the concreteof the piers. Downstream ends of rods 150 are secured to trunniongirders 140 to prevent trunnion girder 140 from being pushed downstreamby the water held back by gate 130. Rods 150 typically extend throughtrunnions 140 to facilitate securing the trunnion girder securely to thepier 120. A typical means of securement is provided by dry-mountedtrunnion base plates 154 positioned on the downstream side of thetrunnion girder. Rods 150 extend through openings in base plates 154 andgripping units 156 are tightened on the rods. In some cases, grippingunits 156 are threaded and engage threaded portions of rods 150. Inother cases gripping units 156 are of the so-called Howlett grip nuttype, for connection to smooth rods. In any case, nuts 156 provide asecure connection of rods 150 to trunnion girders 140 such that the rodportions between trunnions 140 and anchorage means 152 are tensioned. Anuntensioned or free end portion 160 of each rod 150 extends downstreamof each gripping unit 156.

FIG. 1B depicts a trunnion rod system used to secure structurestogether. The trunnion rod system 100 includes a plurality ofpost-tensioned rods 150 extending through a trunnion girder 140 thatapply uniform pressure to affix the trunnion girder to the pier 120 on adam. The trunnion girder 140 is the support that holds that dam gates130 in place, resisting gravity of hydrodynamic forces. The rods 150 arepost-tensioned and “locked off” to maintain their tension to thetrunnion girder 140 by gripping units 156. When the rods 150 areinstalled, they are pulled away from the trunnion girder 140, therebyapplying a tensile force to the rod 150. As the tensile force is appliedto the rod 150 the gripping unit 156 is slid down the rod 150 andtightened to secure the rod 150 to the trunnion 140 without releasingthe tension in the rod 150.

FIG. 2 depicts a gripping unit installed on a rod. The gripping unit 156includes an outer portion 202 that has an opening 204 through the centerof the outer portion 202. The opening 204 has a diameter larger than thediameter of the rod 150 such that the rod 150 can move freely throughthe opening 204. The inner surfaced of the opening 204 includes aplurality of threads 206. An inner gripping unit 208 includes threadscorresponding to the threads 206 on the outer portion 202 of thegripping unit 156. The inner gripping unit 208 has a diameter equal toor slightly larger than the rod 150 such that the inner gripping unit208 is secured to the rod 150 when the inner gripping unit 208 engagesopening 204 of the outer portion 202. In one embodiment, the innergripping unit 208 includes a slit (not shown) extending along one sideof the inner gripping unit 208 to allow the diameter of the innergripping unit 208 to compress when the inner gripping unit 208 is in theopening 204. In another embodiment, the opening 204 is tapered such thatthe diameter of the opening is larger where the rod 150 enters thegripping unit 156 and smaller where the rod 150 exits the gripping unit156.

The inner gripping unit 208 has a height that is smaller than the heightof the outer portion 202. The inner gripping unit 208 includes anopening 210 that is concentric with the opening 204 in the outer portion202. The opening 210 is sized such that the rod 150 fits into theopening 210 when the inner gripping unit 208 is not inserted into theouter portion 202 and the inner gripping unit 208 compresses onto therod 150 when the inner gripping unit 208 is threaded into the opening204 in the outer portion 202 and tension is applied. When installed, theinner gripping unit 208 is positioned in the portion of the outerportion 202 that is farthest from the trunnion 140. A gap having adistance x is formed in the opening 204 below the inner gripping unit208 in the opening 204. When installed, the outer portion 202 can rotatein relation to the inner gripping portion 208 when a rotative force isapplied to the outer portion 202.

FIG. 3 depicts a rod de-tensioning device. The rod de-tensioning device300 includes a gripping unit removal device 302, a chair frame 304, arod tensioning unit 306, a bearing plate 308, a load cell unit 310 and apulling gripping unit 312. The gripping unit removal device 302 includesan opening on an inner surface that engages the outer portion 202 of thegripping unit 156. The gripping unit removal device 302 may be securedto the gripping unit 156 using securing units 314 such as set screws.The chair frame 304 includes four legs 316 that are connected to a topplate 318 with the top plate 318 being parallel to a top surface of thegripping unit removal device 302. The top plate 318 includes an openingthat is sized to accommodate the rod 150 such that the rod 150 passesthrough the opening. The rod tensioning unit 306 includes a centralchannel that allows the rod 150 to pass through the central channel. Therod tensioning unit 306 may be a hydraulic jack that grips the rod 150and applies additional tension to the rod 150 or any other actuationdevice capable of applying a tensile force to the rod 150.

The bearing plate 308 includes an opening that allows the rod to slidethrough the bearing plate 308. The bearing plate 308 is positioned on aside of the rod tensioning unit 306 furthest from the chair frame 304. Aload cell unit 310 is positioned on the bearing plate 308. The load cell310 determines the amount of tension being applied to the rod 150 by therod tensioning unit using known methods. A pulling gripping unit 312 ispositioned on the load cell unit 310 and is secured to the rod 150. Theload cell unit 310 may be any load cell sensor capable of measuring thetensile force in a rod including a load sensor or a strain sensor.

FIG. 4 depicts a drive unit 400 on the chair frame 304. The drive unit400 includes a motor 402 with an engagement unit 404 connected to themotor 402. The engagement unit 404 is configured to engage the sidesurface of gripping unit removal device 302. When the motor 402 isenergized, the engagement unit 404 rotates to loosen or tighten thegripping unit 156 via the gripping unit removal device 302. As thegripping unit 156 is loosened, the gripping unit 156 moves away from thesurface of the trunnion 140 along the inner gripping unit 208 that issecured to the rod 150. By moving the gripping unit 156, a gap x isformed between the original position of the gripping unit 156 and thenew position of the gripping unit 156. When the tension is released fromthe rod tensioning unit 306, the gripping unit 156 moves down thedistance x or a portion of the distance x based on the number of timesthe gripping unit 156 is rotated. When the rod tensioning unit lowersthe tension, the gripping unit 156 moves the bearing surface, and thetension in the rod is reduced at a level relative to the distance x.

FIG. 5 depicts the gripping unit 156 moved from an original position onthe rod 150 to a new position a distance x from the original position.The gripping unit 156 moves along the inner gripping unit 208 whichremains stationary on the rod 150. In one embodiment, a camera ispositioned on the chair frame 304 such that the camera transmits animage representing the position of the gripping unit 156. In anotherembodiment, a first camera is positioned on a side chair unit 304 toview a side view of the gripping unit 156, and a second camera ispositioned on the top of the chair unit 304 to view a top view of thegripping unit 156.

FIG. 6 depicts a rod de-tensioning control unit 600. The rodde-tensioning control unit 600 includes a central processing unit (CPU)602, an input output (IO) unit 604 with the load sensor 310 connected toan input of the IO unit 604 and the drive unit 400 being connected to anoutput of the IO unit 604, a secondary storage device 606 that mayinclude, a communication unit 608 communicatively coupled to a network610, a memory 612. The rod de-tensioning control unit 600 may furthercomprise standard input devices such as a keyboard, a mouse, adigitizer, or a speech processing means (each not illustrated).Additional sensors including temperature sensors, linear verticaldifferential transmitters, pressure sensors, strain sensors and anyother type of sensor may be connected to the IO unit 604. In oneembodiment, video streams from image capture devices, such as a camera,are captured by the IO unit 604 for analysis to determine the amount ofmovement of the gripping unit 156. Consistent with this embodiment, avideo analysis unit residing in the memory 612 may analyze framesextracted from the images sent from the cameras to determine when thegripping unit 156 is moved as well as the distance the gripping unit 156is moved.

In one embodiment, the rod de-tensioning control unit 600's memory 612includes a Graphical User Interface (“GUI”) 614 that is used to gatherinformation from a user via the display device 616 and I/O unit 604 asdescribed herein. The GUI 614 includes any user interface capable ofbeing displayed on a display device 616 including, but not limited to, aweb page, a display panel in an executable program, or any otherinterface capable of being displayed on a computer screen. The GUI 614may also be stored in the secondary storage unit 606. In one embodimentconsistent with the present invention, the GUI 614 is displayed usingcommercially available hypertext markup language (“HTML”) viewingsoftware such as, but not limited to, Microsoft Internet Explorer,Google Chrome or any other commercially available HTML viewing software.

FIG. 7 depicts a schematic representation of the process ofde-tensioning rods using the de-tensioning system 300. In step 702, thegripping unit removal device 302 is placed on the gripping unit 156 suchthat an inner cavity of the gripping unit removal device 302 engages thegripping unit 156. In step 704, the chair frame 304 is slid over the rod150 and placed onto the surface 154 such that the legs of the chairframe 304 are positioned around the periphery of the gripping unit 156.In step 706, the rod tensioning unit 306 is positioned on the rod 150with a first end of the rod tensioning unit 306 being in contact withthe top plate of the chair frame 304. In step 708, a small amount ofhydraulic pressure is applied to the rod tensioning unit 306 to move thehydraulic to simplify the process of disassembling the system after use.to increase the tension in the rod 150. In step 710, the bearing plate308 is positioned on the rod 150 on an end of the rod tensioning unit306 that is furthest from the chair frame 304. In step 712, the loadcell unit 310 is positioned on the rod 150 on the rod tensioning unit306. In step 714, a pulling gripping unit 312 is positioned on the rod150 on the load cell unit 310. In step 716, the pulling gripping unit312 is secured to the rod 150.

In step 718, the drive unit 400 is secured to the chair frame 304 suchthat the engagement unit 404 of the drive unit 400 is positioned on theouter surface of the gripping unit removal device 302. In step 720,hydraulic pressure is applied to the rod tensioning unit 306 to separatethe gripping unit 156 from the trunnion 140. In one embodiment, a cameraunit is positioned on the chair frame 304 to determine when the grippingunit 156 has separated from the trunnion 140. In step 722, the driveunit 400 is actuated to rotate the gripping unit removal device 302causing the gripping unit 156 to rotate along the threads of the innergripping unit 208 such that the gripping unit 156 is moved a distance xfrom its initial position before the drive unit 400 actuated. In step724, the drive motor 400 actuates until the tension in the rod 150 asmeasured by the theoretical distance required to reduce rod tension tothe target level. In step 726, the hydraulic pressure on the rodtensioning device is released. The process of detention the rod 150 maybe performed by the rod de-tensioning control unit 600.

FIG. 8 depicts one embodiment of a gripping unit removal device. Thegripping unit removal device 302 includes a central shaft 800 includingan opening sized to engage the gripping unit 156. A gear unit 802 isaffixed around the periphery of the central shaft 800. The gear unit 802includes a plurality of teeth 804 having a pitch and spacing that aresized to accommodate the engagement unit 404 on the drive unit 400 suchthat the drive unit 400 rotates the gripping unit removal device 302 totighten and loosen the gripping unit 156. In one embodiment, the gearunit 802 is sized to accommodate the engagement unit 404 that hastwenty-four teeth. In one embodiment, a heating unit (not shown) isplaced on the gripping unit removal device 302 to warm the gripping unitremoval device 302 before de tensioning occurs. In one embodiment, theheating unit is a heat tape wrapped around the gripping unit removaldevice 302.

FIG. 9 depicts an arresting unit 900. The arresting unit 900 include amain portion 902 that includes a channel (not shown) with the channelsized to engage a rod 150. The arresting unit 900 includes a spacer 904that extends from one side of the main portion 904. The spacer 904 issized such that it can be inserted between the gripping unit removaldevice 302 and the rod 150 to apply a restricting force on the innergripping unit 208 to restrain the inner gripping unit 208 from rotatingaround the rod 150 during the detensioning process.

In one embodiment, at least one linear vertical differential transmitter(“LVDT”) unit is positioned on the gripping unit removal device 302 todetermine the amount of movement made by the gripping unit removaldevice 302. The LVDT unit may have a rounded end that engages thegripping unit removal device 302. By measuring the distance the grippingunit 156 is moved from its initial position, the amount of tension to beremoved from the rod 150 can be determined. If the amount of tension tobe removed is less than the desired value, the gripping unit 156 may bemoved an additional distance.

In the present disclosure, the words “a” or “an” are to be taken toinclude both the singular and the plural. Conversely, any reference toplural items shall, where appropriate, include the singular.

It should be understood that various changes and modifications to thepresently preferred embodiments disclosed herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present disclosureand without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A method of detensioning a rod, the method including: removablyattaching a gripping unit removal device on a gripping unit where thegripping unit engages a rod; positioning a chair frame on the rod over aperiphery of the gripping unit; positioning a rod tensioning unit on therod with a first end of the rod tensioning unit being in contact with asurface of the chair frame; applying a first force to the rod tensioningunit; positioning a bearing plate on the rod in contact with the rodtensioning unit; positioning a load cell in contact with the rod on therod tensioning unit; securing a drive unit to the chair frame such thata portion of the drive unit is in contact with the rod; applying asecond pressure is applied to the rod tensioning unit; actuating thedrive unit; releasing the second pressure on the rod tensioning unit. 2.The method of claim 1 wherein the first pressure is sufficient toincrease the tension in the rod.
 3. The method of claim 1 wherein thesecond pressure is sufficient to separate the gripping unit from atrunnion.
 4. The method of claim 1 wherein the driving unit includes aengagement portion that is in contact with the rod.
 5. The method ofclaim 1 wherein the drive unit actuates to move the gripping unit apredetermined distance from the trunnion.
 6. The method of claim 1wherein the drive unit is hydraulically driven.
 7. The method of claim 1including connecting a central control unit communicatively coupled tothe drive unit.
 8. The method of claim 7 including optically connectinga plurality of cameras to the central control unit.
 9. The method ofclaim 8 wherein at least one camera is positioned to capture an image ofa side of the gripping unit.
 10. The method of claim 1 wherein the firstpressure is less than the second pressure.